import com.sun.source.tree.Tree;

public class BinarySearchTree {

    static class TreeNode{
        public int val;
        public TreeNode left;
        public TreeNode right;

        public TreeNode(int val){
            this.val = val;
        }
    }

    public TreeNode root;

    //在二叉搜索数中查找key
    //O(logn) O(n)
    public TreeNode search (int key){
        TreeNode cur = root;
        while (cur!= null){
            if (cur.val < key){
                cur = cur.right;
            }else if(cur.val > key){
                cur = cur.left;
            }else{
                return  cur;
            }
        }
        return null;
    }


    //插入
    public void insert(int key ){
        if (root == null){
            root = new TreeNode(key);
            return;
        }
        TreeNode parent = null;
        TreeNode cur = root;
        TreeNode node = new TreeNode(key);

        while(cur!= null){
            if (cur.val <key){
                parent = cur;
                cur = cur.right;
            }else if(cur.val > key){
                parent = cur;
                cur = cur.left;
            }else{
                return;//相同的话就不插入
            }
        }

        if(parent.val > key){
            parent.left = node;
        }else{
            parent.right = node;
        }
    }


    //删除
    public void remove(int key){
        TreeNode cur = root;
        TreeNode parent = null;
        while(cur != null){
            if (cur.val < key){
                parent = cur;
                cur = cur.right;
            }else if(cur.val > key){
                parent = cur;
                cur = cur.left;
            }else{
                removeNode(parent,cur);
                return;
            }
        }
    }

    public void removeNode(TreeNode parent,TreeNode cur){
        if (cur.left == null){
            if (cur == root){
               root = cur.right;
            }else if (parent.left == cur){
                parent.left = cur.right;
            }else{
                parent.right = cur.right;
            }
        }else if(cur.right == null){
            if (cur == root){
                root = cur.left;
            }else if (parent.left == cur){
                parent.left = cur.left;
            }else{
                parent.right = cur.left;
            }
        }else{//要么是左树最右的数替换cur，要么是右树最左的数替换cur，此处以右树为例
            TreeNode target = cur.right;
            TreeNode targetParent = cur;
            while (target.left!= null){
                targetParent = target;
                target = target.left;
            }
            cur.val = target.val;
            if (targetParent.left == target){
                targetParent.left = target.right;
            }else{
                targetParent.right = target.right;
            }
        }
    }
}
